Format code with Runic

[devmotion]

When working on the recent PRs, and in particular the refactoring, it was sometimes a bit difficult to know (or rather guess) how to format code in a way that is seemingly consistent with the existing code.

Hence in this PR I propose to adopt a formatting style. I like Runic, but of course JuliaFormatter could be used as well.

I suggest to exclude the formatting commit (on the master branch) from the git blame history by adding a .git-blame-ignore-revs file in a follow-up PR: https://github.com/fredrikekre/Runic.jl?tab=readme-ov-file#ignore-formatting-commits-in-git-blame

[codecov]

Codecov Report

❌ Patch coverage is 95.65217% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.71%. Comparing base (9d4e9c7) to head (fe8fa99).

Files with missing lines	Patch %	Lines
src/objective_types/nondifferentiable.jl	40.00%	3 Missing ⚠️
src/objective_types/incomplete.jl	93.54%	2 Missing ⚠️
src/objective_types/oncedifferentiable.jl	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #167      +/-   ##
==========================================
+ Coverage   90.69%   90.71%   +0.01%     
==========================================
  Files          10       10              
  Lines         645      646       +1     
==========================================
+ Hits          585      586       +1     
  Misses         60       60              

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